One of the characteristics of ADHD in many people is trouble with initiating tasks, and planning and organization. So, it’s not a surprise that he’s struggling with making plans in advance and initiating planning. If you’re ok with taking on that role in the relationship, I think it’s fine. (We all have strengths and weaknesses).
It’s great that you’re so interested in learning more about ADHD and what his life is like. I just caution you that not everyone exhibits the same symptoms or to the same severity. Don’t judge what your relationship may be like with his specifically, based off what you read about ADHD.
With compassion and understanding, you could have a great relationship with someone with ADHD.
These articles may offer helpful insights for you:
ADDitude Community Moderator, Author & Mentor on Parenting ADHD, Mom to teen w/ ADHD, LDs, and autism